application A language spoken or written by humans, as opposed to a language use to program or communicate with computers. Natural language understanding is one of the hardest problems of artificial intelligence due to the complexity, irregularity and diversity of human language and the philosophical problems of meaning. See also Pleuk grammar development system, proof. An on-line demonstration (http://sakharov.ai.mit.edu/Start). New York U (http://nyu.edu/pages/linguistics/ling.html). (1995-04-24)